486 



THE ARU isuyns. 



[oHjy>. xrxu. 



endeavour to explain. There are three ways in which we 

 may conceive islauda which are not volcanic to have been 

 formed, or to have been reduced to their present condition, 

 —by elevation, by subaidenc*, or by separation from a 

 continent or larj;er island The existence of coral rock, or 

 of raised beaches far inland, indicates recent elevation ■ 

 lagoon coral-islands, and such as have barrier or encircling 

 reefs, have suffered subsidence; while our own islands, 

 whose productions are entirely those of the adjacent con- 

 tinent, have been separated from it. Now the Aru Islands 

 are all coral rock, and the adjacent sea is shallow and full 

 of coral ; it is thertifore evident that they liave been 

 elevated from beDeath the ocean at a not very distant 

 epoch. But if we suppose that elevation to be the first 

 and only cause of their present condition^ we shall find 

 oin-selves quite unable to explain the curious river-chan- 

 nels which divide them. Fissure.^ during upheaval would 

 not produce the regidar width, the regular depth, or the 

 winding curves which characterise thera j and the action 

 uf tides and currents dimni^ their elevation might form 

 straits of irregular width and depth, but not the river-like 

 channels which actually exist. If, again, we suppose the 

 last movement to have been one of subsidence, reducing 

 the size of the islands, these channels are quite as inex- 

 pUcable ; for subsidence would necessarily lead to the 

 Hooding of all low tracts on the banks of the old rivers, 

 and thus oblitemte their courses; whereas these remain 

 perfect, and of nearly uniform width from end to end. 



Now if these channels have ever been rivers they must 

 have flowed fmm some higher regions, and this nsust have 

 been to the east, because on the north and west the sea- 

 bottom sinks down at a short distance from the shore to an 

 unfathomable depth ; whereas on the east a shallow sea, 

 nowhere exceeding fifty fathoms, extends quite across to 

 New Guinea, a distance of about a hundred and fifty miles. 

 An elevation of only three hundred feet would convert the 

 whole of this sea into moderately high land, and make 

 the Aru Islands a portion of New Guinea ; and the rivers 

 which have their mouths at Utauata and Wamnka, might 

 then have flowed on across Am, in the channels which are 

 now occupied by sail water. When the intervening laud 



